Bolt element comprising a shaft part and a spherical head, assembly component and method for producing a bolt element

ABSTRACT

Bolt element ( 10 ) having a shaft part ( 12 ) which is designed at a first end ( 14 ) for a rivet connection ( 16 ) to a panel element ( 18 ), in particular to a sheet metal part, is characterized in that the shaft part ( 12 ) has a spherical formation ( 22 ) at its other end ( 20 ) the ball diameter (D) of which is larger than that of the shaft part ( 12 ). In this manner a bolt element with a spherical head can be manufactured in an extremely favourable manner price-wise and it can be ensured that the spherical head has no burr which would lead to the wearing of the socket provided in operation which slides on the spherical head.

A bolt element of the initially named kind is known from theInternational Application PCT/EP00/06465 or from the correspondingGerman Patent Application 100 33 149.1 as well as from the InternationalApplication PCT/EP00/06468 and from the corresponding German PatentApplication 100 22 152.1.

The present invention relates to a bolt element having a shaft partwhich is designed at a first end for a rivet connection to a panelelement, in particular to a sheet metal part. Furthermore, it relates toa component assembly comprising a bolt element of this kind with acomponent as well as to a method for the manufacture of such a boltelement.

One problem in mechanical engineering is to manufacture favourablypriced bolt elements with a spherical head. Such bolt elements are forexample used as hinge elements for damped spring supports which are usedto support boot lids or bonnets (hoods) of motor cars. Such hingeelements are however also found in a plurality of other constructions,for example in linkages in the actuation mechanism of carburettors andthe like.

The known spherical bolt elements have a thread at the shaft part and aflange projecting radially from the thread so that the bolt element canbe fixedly installed on a sheet metal part or carrier. This design ofthe shaft part of the bolt element also makes it difficult tomanufacture the spherical head because it gives rise: to restrictions inthe design of the cold heading tools for the spherical head.

In the known bolt elements for the spherical head it is problematic thatwhen these are to be manufactured at favourable cost as cold headedparts the movable tool parts which form the spherical head have to moveradially towards the longitudinal axis of the bolt elements and thatburrs form at the surface of the spherical head at the partitionsurfaces, i.e. where these tool parts meet one another, with the burrseach lying in a radial plane. These burrs, even if they are fine innature must either be removed in a costly manner in a further process orone was must accept the disadvantage that the burrs relatively quicklylead to wear of the socket which receives the spherical head,irrespective of whether the socket consists of plastic or metal.

The object of the present invention is to provide a bolt element with aspherical head which can be manufactured at extremely favourable costand nevertheless does not have any disturbing burr. Moreover, afavourably priced attachment of a bolt element to a component should bemade possible, so that the corresponding component assembly can likewisebe obtained at a favourable price. Furthermore, a favourably pricedmethod for the manufacture of a corresponding bolt element is to beprovided.

In order to satisfy this object a bolt element of the initially namedkind is provided with the special characterizing feature that the shaftpart has at its other end a spherical formation, the ball diameter ofwhich is larger than that of the shaft part.

In other words the bolt element in accordance with the inventionconsists essentially of a spherical head and a cylindrical shaft part,which is hollow at its end remote from the spherical head in order toenter into a rivet connection with a panel element, in particular with asheet metal part. Since the diameter of the shaft part is constant, thefunctional element can be manufactured in that a cylindrical blank isreceived in accordance with claim 14 partly in a cylindrical passage ofa die and projects beyond the end face of the die, in that ahemispherical recess is formed in the die in the region of thetransition of the passage into the end face with the ball diameter ofthe hemispherical recess corresponding to the ball diameter of thedesired spherical formation of the bolt element, in that a tool with alikewise hemispherical recess is pressed onto the free end of thecylindrical blank projecting out of the die and the die and the tool arebrought into contact with one another in order to reshape the end of thecylindrical blank projecting out of the die to the spherical formationby cold deformation.

Whereas, in the prior art, the cold heading tools which are used for themanufacture of the spherical head have to be moved in the radialdirection relative to the longitudinal axis of the corresponding blankin the invention the tools, of which there are only two, namely the dieand the tool which cooperates with it, are, so to say, arrangedcoaxially to the cylindrical blank and are moved towards one another inorder to produce the spherical formation by cold deformation of thecylindrical blank. This signifies that in the closed state of the dieand of the tool, i.e. when these contact one another at a partitionsurface this partition surface is located at a position whichcorresponds to an equator of the spherical formation and standsperpendicular to the longitudinal axis of the cylindrical blank or ofthe shaft part of the bolt element.

In this design it is on the one hand possible to guide the die and thetool in such a way that they are strictly aligned relative to oneanother and that only an extremely small burr is formed in the region ofthe equator, if at all. This burr is however also no longer sodisturbing because it does not exert any pronounced scraping action onthe socket on rotating the socket about the longitudinal axis of thespherical head, as is the case of a burr which extends in a radialplane. Because the shaft part of the functional element is made at leastsubstantially cylindrical and has a constant outer diameter, thecylindrical blank can be made at extremely favourable cost fromcylindrical bar material or wire or can be manufactured from tubematerial. A radial movement of the parts of the die or of the tools inorder to take account of the features of shape of the shaft parts is nolonger necessary, since no such features of shape are present in apurely cylindrical shaft part.

Through the design of the rivet connection in accordance with the mannerdescribed in the above-named PCT applications, or in the correspondingGerman patent applications, it is nevertheless possible to secure thecorresponding bolt element at favourable cost and with adequate strengthto a component or to a sheet metal part.

In the first case (in the case of PCT/EP00/06465) the bolt element has aform designed there as a head part in the shape of a hollow cylinderwhich is equipped with piercing and riveting features and which isintroduced in a self-piercing manner into a sheet metal part. In thisarrangement the free end of the hollow head part is formed over to arivet bead at one side of the sheet metal part and the wall of thecylindrical part is formed into a ring fold at the other side of thesheet metal part, so that the sheet metal part is clamped between therivet bead and the ring fold. In this way a stable connection arisesbetween the bolt element and the sheet metal part.

In the second case (in the case of the PCT Application PCT/EP00/06468)the bolt element likewise has a section termed there as the head sectionwhich is again formed as a hollow cylinder but which is strongly roundedat its open end face and thus has in total a cigar-like shape.

In both cases the respective element has an at least substantiallyconstant diameter over its entire length in preferred embodiments.

In the case of the cigar-like element this is not introduced inself-piercing manner into the sheet metal part, but rather the hollowregion of the bolt element is exploited to press the sheet metal partinto a shaping space of a die and is deformed during this into two axialring folds spaced from one another by a ring recess with the sheetmaterial being pressed into the ring recess and thus producing a stablerivet connection between the bolt element and the sheet metal part. Theshaft parts of the respective bolt elements are normally provided withan outer thread. Other formations, such as a peripherally extendinggroove to receive a spring clamp are also described. The disclosures ofthe above designated international applications or of the correspondingGerman applications are also made part of the content of the presentapplication since the designs respectively described there, for therivet connections to the sheet metal part, can be used in identical formin the present invention and represent preferred embodiments of therivet connection which will be used for the present invention.

In both cases the deformation of the hollow region of the shaft part atits first end remote from the spherical head leads to an adequatelybroad ring fold which enables a good attachment to the sheet metal partand so to say forms a broad base so that forces which act in the radialdirection on the spherical head do not lead to a loosening of the boltelement.

Particularly preferred embodiments of the bolt element and also of thecomponent assembly, of the method and also of the die and tools inaccordance with the present invention can be taken from the descriptionof the Figures and also from the subordinate claims.

The invention will now be explained in more detail with reference toembodiments and to the drawing in which are shown:

FIG. 1 a bolt element in accordance with the invention sectioned partlyin the longitudinal direction,

FIG. 2 the tools used in accordance with the invention for themanufacture of the bolt element of the invention of FIG. 1,

FIG. 3 a diagram corresponding to FIG. 5 of the PCT ApplicationPCT/EP00/06465 in order to explain the attachment of the bolt element ofthe invention to a sheet metal part,

FIG. 4 a Figure corresponding to FIG. 2 of the PCT ApplicationPCT/EP00/06468 in order to show the use of the rivet connection of thisPCT Application in the present invention,

FIG. 5 a representation sectioned in the longitudinal direction of aspherical bolt element, which was manufactured from tube material,

FIG. 6 a similar illustration to that of FIG. 6 of a spherical boltelement which was manufactured by means of an internal high pressureforming process,

FIG. 7 a preferred tool for the attachment of spherical bolt elements,

FIG. 8 a detail of the die of FIG. 7 in the region of the rectangledrawn in there without sheet metal part,

FIG. 9 the detail of FIG. 8 after the attachment of the spherical boltelement and

FIGS. 10A to 10D a series of sketches to illustrate different possiblesheet metal preparation steps.

In the following description the same reference numerals will always beused for the same or similar parts and features, so that a descriptionwhich has been given once of a part or of a feature also applies to apart or feature with the same number and the description need not berepeated.

FIG. 1 shows in a side-view a bolt element 10 in accordance with theinvention and having a shaft part 12 which is designed at a first end 14for a rivet connection 16 (see FIG. 3) to a panel element 18 togetherwith a sheet metal part. The shaft part 12 has at its other end 20 aspherical formation 22, the ball diameter D of which is larger than thediameter d of the shaft part.

The diameter d of the shaft part 12 is at least substantially constantover at least substantially its whole length from the sphericalformation 22 up to the end face 24 of the first end 14.

The first end 14 of the shaft part 12 which is designed for the rivetconnection 16 to the sheet metal part is made hollow and has at leastsubstantially the same outer diameter d as the remainder of the shaftpart 12. The hollow space 26 which is formed in this way is, as shown inFIG. 1, at least substantially of circularly cylindrical shape. Thefirst end 14 of the shaft part 12 is formed in a manner known per sewith piercing and riveting features, and indeed in the form of a roundedpunching and drawing edge 28 and has a conical cutting surface 30 at itsinside. The piercing and riveting section of the bolt element 10 is thusformed in accordance with DE-PS 34 470 06 C2. The outer periphery of theshaft part 12 is preferably also made circularly cylindrical, i.e. ithas in cross-section a circular periphery. It would however also beconceivable to use shapes of the shaft part 12 which differ slightlyfrom the circular shape, for example a polygonal shape should thisappear expedient for special reasons.

The hollow region 32 should have a minimum length L (measured in thedirection of the central longitudinal axis 34 of the bolt element 10) toensure that adequate material is present in the hollow region in order,during the formation of the rivet connection 16 of FIG. 3, to form therivet bead 36 at the side 38 of the component 18 remote from thespherical formation 22, to bridge the thickness of the component 18 andto form the ring fold 40 at the side 42 of the component 18 adjacent thespherical formation.

It is also conceivable to make the bolt element hollow as a whole whichwould have the advantage that the element could be manufactured fromtube material and that the spherical formation could be manufactured bya high pressure shaping process inside a corresponding outer die.

When using a hollow shaft part this can optionally be provided with aninternal thread whereby, after formation of the rivet connection of FIG.3 and removal of the stamping slug 44 shown there, a bolt could beintroduced into the thread from the end of the bolt element 10 remotefrom the spherical formation 22 in order to additionally enhance theattachment to the sheet metal part, should this be necessary. A boltelement of this kind could also increase the stiffness of the boltelement itself. With such a design (not shown) it will be necessary toprovide correspondingly shaped washers for a stable seating of the headof the bolt at the underside of the sheet metal part 18 for which itwould be sufficient, under such circumstances, to provide the rivet bead36 with a flattened lower side (in FIG. 3) by a pressing process.

It is moreover evident from FIG. 1 that the spherical formation 22 hasan equator line 46 which lies in a plane which stands perpendicular tothe longitudinal axis 34 of the shaft part. At the position of theequator line 46 there is essentially no burr, i.e. no raised portion tobe found during the manufacture of the bolt element, but rather thisequator 46 merely shows the position of the parting joint of the toolswhich are used to form the spherical formation. These tools are shown inmore detail in FIG. 2. They comprise a lower die 50 and an upper tool52. The designation “lower” and “upper” relates here, as also at otherpoints of the description and claims solely to the alignment of thedrawing and does not represent any restrictions on the actual alignmentof the die or of the tool. These parts could just as easily be arrangedso that the die is disposed above the tool 52 or such that the centrallongitudinal axis 54 is arranged horizontally or in another direction.

The die 50 has a cylindrical passage 56 which merges, in the region ofthe end face 58 of the die, into a hemispherical recess 60 the sphericaldiameter of which corresponds to the diameter D of the sphericalformation 22 of the bolt element 10. Within the central passage 56 ofthe die there is located a cylindrical bar 55, the upper end 64 of whichis located in the hollow space 26 of the bolt element 10 and, forexample, contacts the transverse wall 66 of the hollow space 26. At itsother, lower, end the bar 62 is supported on a firm support, as is thedie 50. The bar 62 is located within a sleeve 68 which can be moved toand fro in accordance with the double arrow 70 in order to eject thefinished bolt element 10 out of the die.

Above the die 50, and coaxially aligned with it, is a tool 52 whichlikewise has a hemispherical recess 74 at its end 70, with thishemispherical recess 74 also merging into a circularly cylindricalpassage 76 which is likewise arranged coaxial to the centrallongitudinal axis 54. The reference numeral 80 points in this embodimentto a cylindrical guide which is located in the passage 76 and the lowerend 82 of which serves to produce the flat 84 at the upper end of thespherical formation 22. This guide 80 can also be biased with a springdevice so that it can deflect by a small amount if, for tolerancereasons, too much material is present for the generation of thespherical formation 22.

The manner of operation of the arrangement in accordance with FIG. 2will now be explained in more detail. Inititally all the bolt element 10should be imagined to be missing. First of all a cylindrical blank (notshown) which has the hollow space 26 and the piercing and rivetingfeatures is introduced into the central passage 56 of the die 50 so thatthe transverse wall 66 is supported on the upper side of the bar 54. Theejection sleeve 68 is retracted in this state so that the lower end face24 of the blank has a distance from the sleeve 68 or can press this awaywith a light contact pressure. The upper die 52 is now guided downwardlyunder the guidance of the guide bar 80 and deforms the upper end of thecylindrical blank into the spherical form 22. At the end of the movementof the tool 52 towards the die 50 the lower end face 72 of the tool 52is in contact with the upper end face 58 of the die 50 and the partitionjoint, i.e. the position at which the end faces 72 and 58 contact oneanother, is so selected that it lies on the equator line 46 of thespherical formation. The cylindrical blank is so dimensioned that itprojects prior to the closing movement of the tool 52 against the die 50beyond the end face 58 of the die 50 and indeed by an amount such thatjust sufficient material is present in order, in the closed state of thetools, i.e. with contact of the end face 72 of the tool 52 against theend face 58 of the die 50 to fill out fully the so formed sphericalspace.

As soon as the tools have reached this closed position the bolt elementis finished, the tool 52 is moved upwardly again and away from the die50 and the sleeve 68 is moved upwardly in order to eject the finishedbolt element 10, as shown in FIG. 2, out of the die 50. Thereafter a newcylindrical blank can be inserted into the passage 56 and the method isrepeated in order to manufacture a further bolt element.

The die 50 can-be arranged in this manufacturing process and the lowertool of a press, whereas the upper tool 52 is attached to the upper toolof the press or to an intermediate platen of the press.

The method for attachment of the bolt element 10 to a sheet metal part18 as shown in FIG. 3 is described in detail in the above-mentioned PCTApplication PCT/EP00/06465 and will not be explained here in furtherdetail because the precise nature and design of the rivet connection isnot the subject of the present invention. Since the lower end of thebolt element 10 is equipped with piercing and riveting features it canbe introduced in self-piercing manner into the sheet metal part 18,whereby the punching slug 44 arises. As shown in FIG. 3 this punchingslug is clamped into the deformed hollow space 26 of the bolt element 10and contributes to the stability of the rivet connection 16. The upperside 90 of the ring fold 40 is so arranged that it lies approximately inthe same plane as the upper side 42 of the sheet metal part 18 and itdoes not therefore present any obstacle for the freedom of movement of asocket placed onto the spherical formation 22. One can see from theshape of the (originally flat) sheet metal part in the region of therivet connection 16 how an extremely stable attachment of the boltelement 10 to the sheet metal part 18 is provided.

The bolt element 10 need not essentially be executed as shown in FIG. 1but rather other designs of the first end 14 are conceivable which arealso suitable for a rivet connection to a sheet metal part. Inparticular a design can be considered as shown in FIG. 2 of the PCTApplication PCT/EP00/06468. This design also enables a rivet connection16′ as shown in FIG. 4 and is likewise realized as set forth in thementioned PCT Application. Advantageous for this type of rivetconnection is the fact that the sheet metal part 18 is not pierced, sothat a water-tight connection is present. As can be read in thecorresponding PCT Application the rivet connection 16′ is effected herein such a way that the hollow region of the bolt element is formed intotwo ring folds and indeed an upper ring fold 40′ and additionally alower ring fold 92 which form a ring-like recess 94 between them. Thesheet metal material is pressed into this ring-like recess 94 by theattachment of the sheet metal element, as shown at 96 in FIG. 4, and isfirmly clamped between the two ring folds 40′ and 92. The referencenumeral 98 points in this example to noses providing security againstrotation which are important in the PCT Application if the correspondingelement has to take up torques about the longitudinal axis.

Since one is concerned here with a bolt element with a spherical head,which does not have to take up any torques, such noses 98 providingsecurity against rotation are not compulsory and the correspondingfeatures of shape of the tools which are necessary to form theses nosesproviding security against rotation can be omitted.

In all embodiments all materials can be named as an example for thematerial of the functional elements which achieve the strength values ofclass 8 in the accordance with the Iso standard in the context of coldforming, for example a 35B2 alloy in accordance with DIN 1654. The soformed fastening elements are suitable, amongst other things, for allcommercially available steel materials for example drawing quality sheetmetal parts and also for aluminium or other alloys.

FIG. 5 shows an axial cross-section through a spherical bolt element 10similar to the spherical bolt element 10 of FIG. 1 but with thedifference that the element was manufactured from tube material and thushas a through-going central passage 100 with a circular cross-section.The lower end of the element of FIG. 5 can be formed in correspondencewith the lower end of the bolt element of FIG. 1 with piercing andriveting features in the form of a rounded pressing and drawing edge 28and a conical cutting surface 30, is however shown here in an embodimentin which the conical cutting surface 30 was reduced to a minimum, whichis also possible. The lower end of the longitudinal passage 100corresponds to the hollow space 26 of the spherical bolt element 10 ofFIG. 1 or forms this hollow space.

The spherical bolt element 10 is manufactured in accordance with thespherical bolt element 10 of FIG. 1 in a tool corresponding to FIG. 2but with the difference, that the guide bar 80 is preferably providedwith a cylindrical projection (not shown) which fits into the centrallongitudinal passage 100 of the tubular blank or of the spherical boltelement and extends downwardly approximately to the upper end of theguide bar 62 in order to support the tube material from the insideduring the formation of the spherical head and to avoid undesireddeformations of the tube material. The step between the bar 80 and thedownwardly directed cylindrical process, which also serves as a guidespigot and is introduced into the central longitudinal passage of theelement forms a radial shoulder which takes care of the flattening 84 atthe upper end of the spherical head.

FIG. 6 shows an alternative design of a spherical bolt element 10 whichis manufactured of tube material. In this case a circularly cylindricaltube section is laid into a two-part die (not shown) which has the outershape of the finished spherical bolt element of FIG. 6 as a hollowcavity. The lower end 24 in FIG. 6 of the spherical bolt element 10 issupported against a transverse wall of a hollow cavity of the mould andhydraulic fluid is forced at high pressure into the interior of the tubesection via the upper end of the tube section in FIG. 6 by means of asuitable nozzle, so that the spherical shape of the spherical head isproduced by the high pressure applied to the inner side. The two-partmould, which is not shown, but which is formed in the region of thespherical bolt elements in accordance with the tool 52 and the die 50has a partition surface between the two halves of the mould at the levelof the plane 102 which is shown in FIG. 6. After formation of thespherical bolt element 10 the mould is opened and the spherical boltelement can be moved from the mould, optionally with the aid of a sliderwhich slides in the axial direction of the shaft part of the sphericalbolt within one of the form halves and preferably presses against thelower end face 24 of the spherical bolt element 10 in FIG. 6.

FIG. 7 shows a preferred tool 104 for the attachment of a spherical boltelement, for example in accordance with FIG. 1, to a plate-likework-piece in the form of a sheet metal part 18. The sheet metal part 18is supported on the upper end face of a die 104 which, in its basicprinciples resembles the dies of the European Patent Application 99 120559.2 and of the European Patent Application 00 931 155.6. In accordancewith FIG. 9 of the first named patent application the die 104 which ispresent here has a hollow body 106 with an end face 108 provided for thesupport of a sheet metal part merging via a conically tapering wall 110into a space having an abutment element 112, with the abutment element112 being spaced from the conically tapering wall for the formation of aring gap 113 which is wedge-like in cross-section.

In the wedge-like ring gap there are a plurality of segment-like shapedparts of the same design, for example from 1 to 8, in particular 4shaped parts 116 which are arranged around the longitudinal axis 118 ofthe die in the wedge-like ring gap 113 and are supported both at theconical wall 110 and also at the abutment element 112. The shaped parts116 can either be so arranged that they completely fill out the ring gap113 around the longitudinal axis 118, i.e. so that no structure ispresent between neighbouring shaped parts 116, for example in accordancewith FIG. 10 of the EP Application 99 120 559.2, or fixed structure ofthe die can be provided between the adjacent shaped parts of the die, asin the die of EP Application 00 931 155.6 or of the earlier related dieof the same inventor.

The abutment element is however designed in this embodiment somewhatdifferently than in the named EP applications.

First of all it is evident that the abutment element 112 has aring-like, radially extending, collar 120 which engages intocorresponding grooves 122 of the shaped parts, with the abutment element112 being movable with the shaped parts in the axial direction 118 ofthe die 104. The lower end 124 of the abutment element projects into ahollow space 126 of the die body 106 and is terminated there with a diskelement 130 screwed on by means of a screw 128. In this hollow space 126there is a compression coil spring between the radially inwardlyprojecting shoulder 132 of the outer part of the die and the die 130,with the compression coil spring being designed to draw the abutmentelement 112 downwardly and also the shaped parts 116 with the abutmentelement 112 via the ring-like collar 120, the maximum downward movementof the shaped parts is bounded by the upper side 134 of the ringshoulder against which the shaped parts enter into contact. This alsorestricts, via the collar 120 and the grooves 122, the lowest possibleposition of the abutment element 122. The upper end 136 of the abutmentelement 122, which can be seen in enlarged form in FIGS. 8 and 9, formsa shaping space 138 for the tubular end 14 of the spherical bolt element10. This ring-like shaping space has a rolling surface 140 ofsemicircular shape in cross-section in its base region which is arrangedsignificantly below the radially inwardly projecting noses 142 of theshaped parts 146. The end face 143 of the central post 144 of theabutment element lies flush with the upper side 146 of the shaped partsin FIG. 8, which in turn lies flush with the upper side of the outerpart 106 of the die 104 and of the tool (not shown), which accommodatesthe die.

The reference numeral 150 points to a ring spring element which holdsthe shaped parts to the abutment element.

As evident from FIG. 8 the shaped parts have rounded edges 152, which isevident from the double line execution.

Whereas, in the die, in accordance with the PCT ApplicationPCT/EP00/06468 the sheet metal part is shaped into a pot-like recessduring the stamping of the corresponding element into a shaping space ofthe die, the central post 144 cooperates with the piercing and rivetingfeatures 28, 30 of the lower end of the spherical bolt element 10 inorder to punch out from the sheet metal part a punching slug 44 similarto the manner described for the shaping die of the German Patent DE-PS34 47 006.

The lower end face 24 of the spherical bolt element punches through thesheet metal part 18 in collaboration with the upper end 143 of thecentral post of the abutment element 12 and draws the sheet metal partaround the hole which is formed in this way over the rounded noses 142of the shaped parts into the shaping space 138 of the die. At the sametime the material of the tubular end of the spherical bolt element 10 isdeflected radially outwardly, and then upwardly again, by the rollingsurface of the abutment element of the die until the free end 24 of thespherical bolt element 10 abuts against the underside 154 of theradially inwardly projecting noses 142 of the shaped parts 116.

One can see from FIG. 9 that the conical shape 156 of the sheet metalpart 18 in the shaping space 130 of the die now lies in form-fittedmanner within the turned over end 14 of the spherical bolt element 10and in that at least essentially the entire shaping space 138 is full ofmetal. As soon as this position is achieved the material of thespherical bolt element can no longer flow into the shaping space 138,the length of the tubular collar is however so dimensioned that thepreviously mentioned ring fold 40 can form, which is shown in FIG. 9.The movement of the free end 24 of the spherical bolt element iseffectively stopped at the lower side 154 of the noses of the shapedparts 116, so that the ring fold 40 can now be formed.

One notes that the punching slug 44 which arose on punching through thesheet metal part is trapped between the upper end 143 of the centralpost 144 and the transverse wall 66 inside the hollow space 26 and therestiffens the connection to the sheet metal part.

During opening of the press after the punching in of the spherical boltelement 10 the spherical bolt element is first lifted and simultaneouslylifts the sheet metal part to which it is now attached, out of the die.In doing so the shaped parts 116 jointly lift upwardly, together withthe abutment element 112, with the coil spring in the hollow space 126being compressed until the forces which act in the region of the rivetbead 36 are sufficient to press the shaped parts 116 radially outwardlyaway from the rivet bead 36, whereby the component assembly consistingof the spherical bolt element 10 and the sheet metal part 18 are freedfrom the die 104.

The upper part 160 of the tool 104 of FIG. 7 represents a setting headwhich is designed for the attachment of the spherical bolt element suchas 10 to the sheet metal part 18 and for this purpose can be attachedvia a holder, not shown, to an upper tool 163 of a press or to anintermediate platen of a press or, in an inverse arrangement, to a lowertool of the press.

The setting head 160 is aligned here in order to achieve a centralalignment of the spherical bolt element with the die and prevents akinking of the bolt element when it is stamped into place. The dieensures a termination of the beading operation when the free end face 24of the rivet bead 36 runs against the die insert, i.e. against theshaped parts 116 and thus a defined starting point for the bulging outof the shaft 16 for the formation of the ring flange 40 and indeed evenwhen only one shaped part 116 is provided, which is fundamentallypossible with a die construction similar to the EP application 00 931155.6.

The setting head 160 has an outer tubular part 162 with a conical recess164 at the lower end 166 in which, in turn, a plurality of shaped parts,for example four shaped parts 168, are accommodated of which only theone shape part 168 is visible in FIG. 7. The shaped parts each have aconical outer wall 170 which is made complementary to the conical wall164 of the outer part 162 of the setting head 160.

In the lower region of the shaped parts in FIG. 7 these have radiallyinwardly extending jaw faces 172 which engage on the shaft part 14 ofthe spherical bolt element 10 and are formed as part-cylindricalsurfaces so that an areal contact at the spherical bolt element ispossible, in order to ensure the required alignment of the sphericalbolt element 10 with the central longitudinal axis 174 of the settinghead, which stands coaxial to the central longitudinal axis 118 of thedie.

In the upper region the shaped parts 168 have radially inwardly directednoses 176 which extend into a groove 180 in a displaceable sleeve 182 ofthe setting head 160. The lower boundary 184 of the groove engagesbehind the noses so that the shaped parts 168 are compulsorily guided,i.e. axially movable with the sleeve 182.

A ring spring 184 surrounds the shaped parts 168 and thus ensures thatthe shaped parts 168 are not lost. The sleeve 182 has in its upperregion a radially outwardly directed collar 186 which is movable in acircularly cylindrical hollow space 188 of the outer part 162 of thetool 160, with a radially inwardly directed ring shoulder 190 of theouter part 162 of the tool 160 bounding the hollow cavity 188 at thebottom and forming an abutment for the radially outwardly directedcollar 186 of the sleeve 182.

Within the upper region of the sleeve there is located a lightcompression coil spring 192, the lower end 194 of which contacts aradially inwardly directed shoulder 196 of the sleeve 182 and the upperend of which in FIG. 7 is braced against the upper tool 163 of thepress. In this embodiment the spring thus lightly biases the sleeve inthe direction radially downwardly.

A plunger pin 200 with a conical upper end 202 is located within acylindrical bore 198 of the sleeve 182 in the lower region of the sleeveand is supported against a corresponding conical surface within thedisplaceable sleeve 182, so that the plunger pin 200 cannot falldownwardly out of the sleeve 182. Above the plunger pin 200 there is agrub screw 204 which is screwed into a threaded bore 206 of thedisplaceable sleeve to prevent the plunger pin 200 deviating upwardly.The screw connection between the grub screw 204 and the sleeve 182ultimately also transmits the pressure forces, which coming from theupper tool 163 of the press, press the sleeve 182 and thus also the grubscrew 204 and the plunger pin 200 downwardly. One can see that theplunger pin 200 comes into contact on the flat 84 at the upper end ofthe spherical bolt element 10.

On closing the press the spherical bolt element cannot deflect upwardlyand the downwardly directed forces lead to the above described piercingof the sheet metal part and also to the shaping of the lower end 14 ofthe spherical bolt element 10 and the formation of the ring fold 40.When these shaping operations are concluded the lower end 16 of theupper tool 160 contacts the sheet metal part 18 and presses the latteragainst the lower tool in the form of the die 104.

On opening of the press the upper tool 160 lifts the spherical boltelement 10 with the attached sheet metal part 18 out of the die so thatthe die releases the component assembly, as described above. The sheetmetal part then strikes against other parts of the press (not shown) sothat a downwardly acting force is exerted on the spherical bolt element.The spherical bolt element thus pulls the shaped parts partly out of theouter part of the upper tool to such an extent that the outwardlyextending collar 186 comes into contact with the radially inwardlydirected ring shoulder 190. This axial movement is sufficient in orderto release the spherical head from the shaped parts 168 since these candeflect radially outwardly when they are partly pulled out of the outerpart of the upper tool. In order to favour this radially outwardlydirected movement the shaped parts 168 have in the region of the axialupper ends of the jaw surfaces 172 inclined faces or shaped faces 208which cooperate with the rounded spherical surface of the spherical headof the spherical bolt element.

The component assembly comprising the spherical bolt element and thesheet metal part can now be removed from the working area of the tool inaccordance with FIG. 7.

Since the compression coil spring holds the shaped parts in the openedposition a new spherical bolt element can be introduced from below intothe upper tool and pressed upwardly (until the jaw surfaces 172 of theshaped parts again engage the shaft part 14 of the spherical boltelement 10 and the compression coil spring is compressed. The ringspring 205 which, for example consists of polyurethane and which pressesthe shaped parts 168 towards one another is made sufficiently strong tohold the sleeve 182 with the shaped parts 168 in the position shown inFIG. 7 by friction at the conical wall 164. The new spherical boltelement now adopts the position of the spherical bolt element 10 of FIG.7.

A new sheet metal part 18 can now be introduced into the press and, asdescribed previously, the new spherical bolt element can then be rivetedto the new sheet metal part 18.

Instead of inserting the bolt element from below, for example by hand,between the shaped parts or shaped segments 168 of the upper tool thespherical bolt elements 10 can be introduced in an automated embodimentthrough an obliquely aligned guide channel 210 into the space betweenthe shaped parts.

If for example three shaped parts 168 are provided, the obliquelyaligned guide passage can lead into the intermediate space between twoof the segment-like shaped parts 168. This makes it possible for thespherical bolt element 10 to move from the obliquely aligned position ofthe guide passage 210 into the vertically aligned position between theshaped parts 168. A similar procedure is however also possible if thetool 160 is provided with four contacting shaped parts 168, providingthe necessary space for the guide passage 210 can be created.

The series of sketches 10A, 10B, 10C and 10D finally show that it isalso possible to insert the spherical bolt element into thicker piecesof sheet metal. With sheet metal of approximately 1.5 mm thickness it issufficient to pierce the sheet metal part 18 or, as is shown in FIG.10A, to pre-form a hole as at 212.

For sheet metal thicknesses beyond 1.5 mm it is however favourable tocarry out a sheet metal preparation step so that the sheet metal has theshape of FIG. 10B in the region of the hole 214. A sheet metalpreparation of this kind is for example described in connection with theso-called clamping hole riveting process (European Patent 539 793) andin connection with the so-called EBF elements in the PCT ApplicationPCT/EP96/04188, which is why it is not repeated here. FIG. 10C showsthat the inner diameter of the hole 215 corresponds during thepreforming of the hole and preparation of the sheet metal part at leastsubstantially to the outer diameter d of the lower end 14 of thespherical bolt element. FIG. 10D finally shows the position after theattachment of the element which is executed according to the PCTApplication PCT/EP00/06465.

The possibility also exists of using the die of FIG. 7 to attach thebolt element into the prepared sheet metal part, with no punching slugarising here because the sheet metal part is not pierced by thespherical bolt element. The installation situation presents itselfsimilarly to that of FIG. 10D except that a nip is present between thebeaded over end 24 of the rivet bead 36 and the sheet metal part whichis produced by the noses 142 of the shaped parts 106 of the die 104.

1. Bolt element having a shaft part with first and second ends, saidshaft part being connected at said first end with a rivet connection toa panel element, wherein the shaft part has a spherical formation with aball diameter at said second end, said shaft part having an at leastsubstantially constant diameter over at least its total length from saidspherical formation up to said first end and said ball diameter beinglarger than said shaft diameter.
 2. Bolt element in accordance withclaim 1, wherein the first end of the shaft part which is designed forthe rivet connection to the panel element is made hollow and has atleast substantially the same outer diameter as the shaft part.
 3. Boltelement in accordance with claim 2, wherein the first end of the shaftpart is formed with piercing and riveting features.
 4. Bolt element inaccordance with claim 3, wherein the hollow first end of the shaft partmerges from a right cylindrical jacket surface into a rounded pressingand drawing edge and has a conical cutting face at the inside.
 5. Boltelement in accordance with claim 2, wherein the inner space of thehollow first end of the shaft part is made at least substantiallycircularly cylindrical.
 6. Bolt element in accordance with claim 2,wherein the hollow region of the shaft part at the first end is made atleast sufficiently long that adequate material is present in the hollowregion in order to form a rivet bead at the side of the component remotefrom the spherical formation, to bridge the thickness of the componentand to form a ring fold at the side of the component adjacent to thespherical formation.
 7. Bolt element in accordance with claim 1, whereinthe entire bolt element is made hollow.
 8. Bolt element in accordancewith claim 1, wherein the hollow shaft is provided with an internalthread.
 9. Bolt element in accordance with claim 1, wherein thespherical formation has an equator line which lines in a planeperpendicular to the longitudinal axis of the shaft part.
 10. Componentassembly formed from a bolt element and a panel element, said boltelement having a shaft part with first and second ends, said shaft partbeing connected to said panel element by a rivet connection at saidfirst end and having a spherical formation with a ball diameter at saidsecond end, said shaft part having an at least substantially constantdiameter between said rivet connection to said panel element and saidsecond end, said ball diameter being larger than said shaft diameter andsaid rivet connection comprising a rivet bead located at a side of saidpanel remote from said spherical formation and a ring fold arranged at aside of said panel adjacent said spherical formation, with said panelbeing clamped in the region of said rivet connection between said ringfold and said rivet bead.
 11. Component assembly in accordance withclaim 10, wherein the ring fold is arranged in a ring recess in thesheet metal part, with a ring surface of the ring fold adjacent to thespherical formation either being arranged fractionally below orfractionally above the side of the sheet metal part adjacent the shaftpart in the region of the rivet connection or at the same level as thisside of the component.
 12. Component assembly in accordance with claim10, wherein a punching slug is trapped inside a bead and thus pressesagainst the latter.
 13. Method of manufacturing a bolt element inaccordance with claim 1 having a shaft part which is designed at a firstend for a rivet connection to a panel element, in particular to a sheetmetal part and having, at its other end, a spherical formation, the balldiameter of which is larger than that of the shaft part, wherein acylindrical blank is partly received in a cylindrical passage of a dieand projects beyond the end face of the die, in that a hemisphericalrecess is formed in the die in the region of the transition of thepassage into the end face, with the ball diameter of the hemisphericalrecess corresponding to the ball diameter of the desired sphericalformation of the bolt element, in that a tool with a likewisehemispherical recess is pressed onto the free end of the cylindricalblank projecting out of the die and the die and the tool are broughtinto contact with one another in order to reshape the end of thecylindrical blank projecting out of the die to the spherical formationby cold deformation.
 14. Method in accordance with claim 13, wherein, inthe closed state of the die and of the tool, these contact one anotherat a partition surface which corresponds to an equator of the sphericalformation and stands perpendicular to the longitudinal axis of thecylindrical blank, i.e. of the shaft part of the bolt element.
 15. Boltelement according to claim 10, wherein the panel element is a sheetmetal part.